The invention relates to a semiconductor device having a semiconductor body which includes a field effect transistor and which is partly covered with an insulating layer, said semiconductor body comprising an active transistor region with a number of semiconductor zones of the one conductivity type which are embedded in the semiconductor body and which adjoin the surface thereof, said semiconductor zones forming two electrode zones, one of which surrounds the other, and at least one island zone which is situated therebetween, thus enclosing channel regions of the opposite conductivity type. On the insulating layer above the channel regions there are provided gate electrodes, a first gate electrode thereof surrounding a second gate electrode, said gate electrodes being connected respectively to a first and a second bond pad which are provided on the insulating layer, the first bond pad being situated outside the active transistor region.
A semiconductor device of this kind is particularly suitable for use as an amplifier element in high-frequency preamplifiers of television receivers. A signal received by the television antenna is applied to the first gate electrode of the transistor, the second gate electrode being connected to a variable direct voltage source. By variation of the value of the direct voltage on the second gate electrode, the gain of the transistor can be adjusted so that amplified signals have a substantially constant amplitude.
From Netherlands Patent Application No. 6910195, laid open to public inspection, a semiconductor device of the kind set forth is above known in which the gate electrodes form closed loops. The outer loop (the first gate electrode) is connected to the bond pad which is situated outside the active transistor region, the inner loop (the second gate electrode) being locally widened in order to form a bond pad which extends over a part of the island zone which is also locally widened.
A field effect transistor of this kind exhibits a high transconductance and a low input attenuation. The transistor, however, has the drawback that the second bond pad is situated over a part of the island zone. Such a bond pad has a comparatively large surface area, so that a comparatively high capacitance exists between the island zone and the first gate electrode. Due to this capacitance, the gain of the transistor decreases as the frequency of the signal to be amplified becomes higher.